What does the speed graph in your Telraam statistics mean?
To begin with, it's important to know that speed statistics are indicative. Measurements may differ by 10% from effective speeds.
The figure shows, in a bar chart, the percentage of the cars per speed level, for the period you have selected at the top of the page.
How accurate is this?
We don't know exactly. These figures are not compared to a calibrated speedometer. Theoretically, we expect there to be a limited error for properly functioning Telraam devices, if you look at them for a sufficiently large time interval. The speeds are primarily indicative and provide a good basis for comparison with other streets.
According to my Telraam, cars drive faster than 70km/h in my street, but that's not possible physically. The statistics also indicate that some cars drive at less than 10 Km/h. Is my Telraam not working?
No, but there are so-called outliers; measurements in which something has gone wrong. We don't filter for these errors.
If the statistics indicate that a number of cars are travelling at less than 10 km/h, the explanation is probably a misclassification. For example, groups of cyclists that are classified as cars. You want to know more about this classification? You can read it here: "How does the Telraam classification work?"
If you suspect that there is a problem with the speed measurements, report it to the Telraam team by sending us a mail at email@example.com
Is my Telraam a speed camera after all?.
No, certainly not. Your Telraam cannot make a statement about the (calibrated) speed of individual cars. The measurement error can be large at the level of individual vehicles, but that error can be in both directions (faster or slower than in reality). This error corrects itself at the level of a group of cars, as there are more measurements. Telraam can therefore give you an idea about the speed regime of a large number of vehicles.
What about large vehicles?
Telraam cannot measure the speed for large vehicles because the measurement assumes that objects within one group have the same typical length. This is relatively true for cars (the length of any given car will always be very close to the "typical car length"), but larger vehicles range from larger SUVs to long trucks and buses, which is a very broad scale for length.